They bring this genetic material to the Mother Grub, who combines it all in an incestuous slurry and lays hundreds of eggs at once - genetic material from stronger bonds of either nature see more representation in the resulting brood, while weaker relationships result in more recessive genetic traits. We should all take a moment to lament how pedestrian the human reproductive system is, and further lament that the phrase "incestuous slurry" is not a feature of common parlance in human civilization.